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Reverse Engineering the Macintosh SE PCB & Custom Chips for 1:1 reproduction


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On 1/16/2021 at 5:40 PM, Kai Robinson said:

but for now the missus is groaning at me to turn the lights off and come to bed...and we all know that happy wife = happy life :D

 

This and many reasons is precisely why im not married, and love being independent. 

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22 hours ago, Kai Robinson said:

Awesome ! Where did you find that ?

So, in theory, verifying the components one by one using the Bomarc schematics would be enough to find the issues with your board, right ?

If you can forward me a board, that's definitely something I can do ! ;)

Edited by timdorez
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@timdorez

 

You'd probably want to be checking for shorts as well as continuity - which would be quite time consuming, but if you did we'd find anything.

 

Also at some point we might have issues with chip timings - sometimes chips of different grades or even just from different manufacturers don't work in a circuit because they're too slow / too fast. Best to start with as many reappropriated chips to start as long as they don't get damaged.

 

On that subject - @Kai Robinson do you have one of these (random listing, shop around)? If not, get one!

https://www.ebay.co.uk/itm/New-IC-Tester-74-40-45-Series-lC-Logic-Gate-Tester-Digital-Meter-/271634652740

 

Also, these are useful :

https://www.ebay.co.uk/itm/LCR-TC1-Transistor-Tester-ESR-Capacitance-Meter-Electronic-Component-NPN-PNP-/353176611089?

 

Available from UK sellers too.

 

Edited by Phipli
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2 hours ago, Phipli said:

On that subject - @Kai Robinson do you have one of these (random listing, shop around)? If not, get one!

 

Also worth noting that if one has a TL866 II programmer, which seem to be rather widespread, it has a logic chip test mode in it as well, which has worked better than I was expecting when I've used it, anyway.

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2 hours ago, cheesestraws said:

 

Also worth noting that if one has a TL866 II programmer, which seem to be rather widespread, it has a logic chip test mode in it as well, which has worked better than I was expecting when I've used it, anyway.

Fair point - I have both and got the tester first. Still handy as it doesn't need a computer, but not worth purchasing if you have an TL866.

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2 hours ago, Phipli said:

Fair point - I have both and got the tester first. Still handy as it doesn't need a computer, but not worth purchasing if you have an TL866.

 

Yup.  More that I didn't find the logic tester feature until some considerable time after I had bought the programmer, so wanted to flag it up in case anyone else is as oblivious as I am :-).

Edited by cheesestraws
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14 hours ago, timdorez said:

Awesome ! Where did you find that ?

So, in theory, verifying the components one by one using the Bomarc schematics would be enough to find the issues with your board, right ?

If you can forward me a board, that's definitely something I can do ! ;)

 

Thanks to Johan Grip on the Retro Tinkering discord - he located them here: https://www.macintoshrepository.org/28274-mac-se-schematics

Would you like a blank board to build up?

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I'd guess probably the most useful thing from @timdorez's tech manuals is the troubleshooting info, seems like the other schematics are largely the same as what currently floating around but always worth taking a more detailed look!

 

Nice find on the Bomarc Macintosh SE schematic... macintoshrepository.org is a pain to deal with and yeah it's understood that the Bomarc schematics didn't make it out to public on good terms, but... well, it's info that can be digested into a schematic redraw under better terms, in a different style and format.  I'll probably get around to doing full schematic redraws in the KiCad style similar to the SE/30, but for all of the SE, Plus, and 128k/512k.

 

But what's somewhat a bummer about this... sure you can create the ideal knowledge repository, but as most of our community primarily interacts via search engines, it won't make it out to search engine results until years later.  Well, no hurry on that I guess.

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On 1/19/2021 at 4:41 PM, quorten said:

I'd guess probably the most useful thing from @timdorez's tech manuals is the troubleshooting info, seems like the other schematics are largely the same as what currently floating around but always worth taking a more detailed look!

 

Nice find on the Bomarc Macintosh SE schematic... macintoshrepository.org is a pain to deal with and yeah it's understood that the Bomarc schematics didn't make it out to public on good terms, but... well, it's info that can be digested into a schematic redraw under better terms, in a different style and format.  I'll probably get around to doing full schematic redraws in the KiCad style similar to the SE/30, but for all of the SE, Plus, and 128k/512k.

 

But what's somewhat a bummer about this... sure you can create the ideal knowledge repository, but as most of our community primarily interacts via search engines, it won't make it out to search engine results until years later.  Well, no hurry on that I guess.

how is progress with revamped boards? Were you able to fix all the traces and get a proper 1:1 repro yet? Btw I noticed with one of the pictures that was uploaded where some traces went to vias where they should have just been straight traces, there was one section that was circled that needed to be fixed where the trace to the left of it had a similar problem, but I’m not sure if you noticed it or not. 

 

if there is some way I can help such as comparing high res photos or the repro boards and the original to ensure the traces are correct and there are no connected vias where there shouldn’t be any, I’m happy to give it a look and be another set of eyes to ensure faithful reproduction of these boards. 
 

I am extremely excited for the SE/30 version to be done eventually. The SE/30 is my dream computer. I’m rocking a Mac classic I repaired and brought back from the dead. (I even was able to get a modern scsi/3 15k rpm server drive to work on the 50-pin stock scsi bus to work on the Mac classic. I have some other issues with the comp though. I think the external scsi port and the serial port/chip has some issues which causes the computer to crash if an external scsi drive or the AppleTalk plugs are plugged into the back of the machine along with an audio issue I can’t seem to resolve. I have no audio at all on the computer and I think it’s due to the battery that destroyed part of the board. 
 

id love to start making and selling rascsi HD’s with raspi zeros to help people replace HD’s instead of the 15k server hd I used. Plus the scsi2sd is too expensive of a replacement for these comps. If I can make a rascsci affordable (around 20$) I think it’ll go a long way to help preserve these beautiful machines. I think many people who get these comps to refurb them don’t realize how much of a pain getting replacement HD’s can be. Anyway I’ve drones on enough. Let me now how I can be of service and make this project gain any more progress. Thanks.

 

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5 hours ago, DrewNucci said:

how is progress with revamped boards? Were you able to fix all the traces and get a proper 1:1 repro yet? Btw I noticed with one of the pictures that was uploaded where some traces went to vias where they should have just been straight traces, there was one section that was circled that needed to be fixed where the trace to the left of it had a similar problem, but I’m not sure if you noticed it or not. 

 

if there is some way I can help such as comparing high res photos or the repro boards and the original to ensure the traces are correct and there are no connected vias where there shouldn’t be any, I’m happy to give it a look and be another set of eyes to ensure faithful reproduction of these boards. 
 

I am extremely excited for the SE/30 version to be done eventually. The SE/30 is my dream computer. I’m rocking a Mac classic I repaired and brought back from the dead. (I even was able to get a modern scsi/3 15k rpm server drive to work on the 50-pin stock scsi bus to work on the Mac classic. I have some other issues with the comp though. I think the external scsi port and the serial port/chip has some issues which causes the computer to crash if an external scsi drive or the AppleTalk plugs are plugged into the back of the machine along with an audio issue I can’t seem to resolve. I have no audio at all on the computer and I think it’s due to the battery that destroyed part of the board. 
 

id love to start making and selling rascsi HD’s with raspi zeros to help people replace HD’s instead of the 15k server hd I used. Plus the scsi2sd is too expensive of a replacement for these comps. If I can make a rascsci affordable (around 20$) I think it’ll go a long way to help preserve these beautiful machines. I think many people who get these comps to refurb them don’t realize how much of a pain getting replacement HD’s can be. Anyway I’ve drones on enough. Let me now how I can be of service and make this project gain any more progress. Thanks.

 

 

Tomorrow is the day of hopefully more progress - today has been a day to just relax after the tough week i've had! I've got some multicoloured solid core wire to hook up to the board in various places for ease of monitoring signals - i really really want a DIP64 test clip for my logic analyzer!

I'll post the updated Sprint file in a sec actually, the image files were already shared a page or two prior. 

Which traces went to via's btw? If you've noticed them i'll compare them to the sprint layout. 

MacintoshSE.lay6

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Hmm, i've redone some of the traces around the SND/Serial SCC stuff - i discovered that the 26LS32 is not correctly connected! There's a tiny trace that goes from Pin 1 (1B inverting input) to a via, and i missed that - having that unconnected could be throwing off stuff...it's a longshot, but i can try...i'm basically going over every via/trace on the sprint layout, ensure that nothing is unconnected - plus lining stuff up a little better - has no effect on the signalling, but I like things to be as neat as possible :D

Edited by Kai Robinson
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Some good news, despite my failures of desoldering (lesson learned), @ymk assisted me in repairing the issues with the board and correcting the breakout issues.  Now, we have a fully functional board with breakout.  @ScutBoy was kind enough to lend his Brainstorm system (don't worry I used my own logic board) so I'll be sending that to @asicsolutions.  He is very busy wrapping up the Micron Xceed project so I wouldn't expect results for quite some time.  If/when I have an update I'll post it.  

20210129_233419.jpg

20210129_233435.jpg

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Mentioning bodge wire and unconnected traces that shouldn't affect signaling... well that's one thing that old and slow computers are quite a bit more forgiving on!  If I've read the schematics correctly, though, the Macintosh SE does in fact use some impedance-matching resistors for certain high frequency signals like the clock lines, RAM RAS, RAM CAS, and RAM WE... so that could be a hint to scrutinize the quality on those lines.

 

@Kai Robinson Alright, I think I have another thought looking at the board photos in detail.  I noticed R33A, yes a 47 ohm impedance-matching resistor on a RAM CAS line, might have a soldering quality issue.

board_inspect.jpg

Edited by quorten
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I just discovered male PLCC 84 adapters that might have saved a fair bit of trouble. Those could be good for building a PCB in the future though. 
 

Does anyone know a “cheap” logic analyzer that has at least 84 channels and that a novice like me can capture/store data and sent to someone more qualified? This could save a fair bit of trouble.

C862427B-D3C1-4ADC-AAE5-17B3A781E0A6.jpeg

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Check your local craigslist for vintage HP logic analyzers. For example, last month on my local craigslist there was an HP 1660B (136 channels) for $100, though only had enough probes for 68 channels. You can find additional 34 channel probes on eBay for $30 or so. Currently there is an HP 1651B (102 channels) with a full set of probes for $120. These are '90s professional logic analyzers. They have 250 MHz timing speed and 100 MHz state speed, which make them extremely capable for retro applications.

 

HP 16x0 analyzers have 136 channels, 16x1 have 102, 16x2 have 68, and 16x3 have 34. The 'x' is the generation. The entire series had the same performance specs (250 MHz), basically over time they added more convenience features, more memory depth, etc.

 

You might also see Tektronix logic analyzers which would be suitable, but I don't know what models to look for from Tektronix.

Edited by anthon
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There are also the HP 16500 and 16700 series that you might come across. They are much larger and use an expansion card system for all logic and scope functions, so you have to check which cards it comes with.

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9 hours ago, quorten said:

Mentioning bodge wire and unconnected traces that shouldn't affect signaling... well that's one thing that old and slow computers are quite a bit more forgiving on!  If I've read the schematics correctly, though, the Macintosh SE does in fact use some impedance-matching resistors for certain high frequency signals like the clock lines, RAM RAS, RAM CAS, and RAM WE... so that could be a hint to scrutinize the quality on those lines.

 

@Kai Robinson Alright, I think I have another thought looking at the board photos in detail.  I noticed R33A, yes a 47 ohm impedance-matching resistor on a RAM CAS line, might have a soldering quality issue.

board_inspect.jpg


Ooh, good catch, i'll check that. 

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